While in Safe Mode, go to Start/ Run/ type SFC in the box and click OK.
This will check your System Files.
You will need your system CD if any files are corrupt and need replacing.
You could also right click MY COMPUTER on the desk top/ left click Properties/ Device Manager and see if there are any yellow exclamation marks.
A yellow mark means you have a problem with the item.
See how you go with the above.